As used herein, the term "circuit module" refers to an interconnection substrate such as a printed circuit board (PCB) having electronic components mounted thereto. A PCB is a multi-layer substrate, having alternate layers of insulating material and conductive material. The conductive material is patterned to have conductive "lines" or "traces" for routing signals (and power) from one location on the PCB to another location on the PCB. Electronic components are interconnected with one another by the conductive traces. Conductive traces may be disposed on both sides (surfaces) of the PCB. Examples of electronic components which may be incorporated in a circuit module include:
(a) "active" electronic components such as integrated circuit (IC) devices, and the like; PA1 (b) "passive" electronic components such as resistors, capacitors, and inductors (including transformers), and the like; PA1 (c) switches, relays and the like; and PA1 (d) sensors, transducers and the like.
In some cases, a circuit module is intended to be disposed in a "harsh" environment, and it is desirable to isolate the electronic components of the circuit module from such an environment. An example of such an application for a circuit module is an RF transponder which is disposed within a pneumatic tire of a vehicle. In such applications, it is generally desirable to encapsulate or otherwise package the circuit module to isolate the electronic components from the environment.
As used herein, a "transponder" is an electronic apparatus (device) capable of monitoring a condition such as air pressure within a pneumatic tire, and transmitting information (a signal) indicative of the monitored condition to an external device. The external device can be either an RF (radio frequency) reader/interrogator or, simply an RF receiver. A simple receiver can be used when the transponder is "active", and has its own power source. A reader/interrogator would typically be used when the transponder is "passive" and is powered by an RF signal from the reader/interrogator. In either case, in conjunction with the external device, the transponder forms a component of an overall tire-condition monitoring/warning system.
In order to send and receive RF signals, a transponder must have an antenna. The antenna may either be incorporated into the transponder module itself, or it may be external to the transponder module and electrically connected or coupled to it in a suitable manner.
U.S. Pat. No. 4,724,427 (Carroll; 1988), incorporated in its entirety by reference herein, discloses a transponder device. FIG. 9 of the patent, shows a topographical representation of a transponder chip (100) in an embodiment that includes an antenna coil (104) as part of a monolithic chip (102). As disclosed therein, the coil (104) is etched around the periphery of the monolithic chip also known as the chip substrate (102). In the center of the coil (104) are found a custom logic circuit (106), a programmable memory array (108), and a memory control logic (110). Using the chip topography shown in this figure, a functionally complete transponder may be realized on a single semiconductor chip. (see column 11, lines 7-22; numbers edited)
In a similar manner, U.S. Pat. No. 5,345,231 (09/1994) discloses a contactless inductive data-transmission system. FIG. 7 of this patent shows components of a chip having a substrate (52) which can be photolithographically deposited along with antenna coils (50) which can be in a plane above the semiconductor topography (51) of the chip. (column 7, lines 14-17) In both this patent and the aforementioned U.S. Pat. No. 4,724,427, the antenna coils are disposed around the periphery of the IC chip, surrounding the components and periphery of the IC chip.
U.S. Pat. No. 5,574,470 (de Vall; 1996), incorporated in its entirety by reference herein, discloses a radio frequency identification transponder apparatus and method. A transponder is formed of a very thin flexible dielectric substrate (10) on opposite sides of which are formed first (26) and second (31) series-connected halves of a single antenna coil having ends connected to an integrated circuit die (50) mounted to a die bond site (46) at a corner of the substrate (10). Conductive vias (22,24) extend through the substrate (10) to effect connection between the antenna halves (26,31), from one side of the substrate to the other side of the substrate. Protective laminates (58,60) on either side of the substrate (10) are bonded to one another around the substrate edges, and also are bonded to one another at interior portions through a slot (20) formed in the substrate (10).
The following patents, all of which are incorporated in their entirety by reference herein, are cited as being of interest: U.S. Pat. Nos. 5,923,300; 5,894,006; 5,879,502; 5,870,066; 5,854,480; 5,461,545; 5,420,757; 5,345,231; 5,313,365; 5,250,843; 5,223,851; 5,218,861; 5,214,410; 5,181,975; 4,911,217; 4,851,855; 4,795,693; 4,724,427; 4,628,148; 4,524,324; and 4,092,487.